Lab 5 Report

Experiment 5 – K sp of Ca(OH) 2 – Post-lab Worksheet Results and Calculations Table 1. Experimental data. Concentration of HCl (M): 0.0199 M Room Temperature Actual temperature (K) 293.25 K 1/T (1/K) 1 293.25 𝐾 Initial burette reading (mL) 9.8 mL Final burette reading (mL) 20.7 mL Volume titrated (mL) 10.9 mL Sample volume (mL) 5.0 mL Moles of HCl titrated (mol) 0.0199 mol Concentration of OH – (mol/L) 0.0434 mol/L Concentration of Ca 2+ (mol/L) 0.0217 mol/L K sp 4.1 x 10 -5 lnK sp -10.10 ΔG° (kJ/mol) 24.63 kJ/mol 60 – 80 °C Actual temperature (K) 348.55 K 1/T (1/K) 1 348.55 𝐾 Initial burette reading (mL) 20.7 mL Final burette reading (mL) 31 mL Volume titrated (mL) 10.3 mL Sample volume (mL) 10 mL Moles of HCl titrated (mol) 0.0199 mol

Concentration of OH – (mol/L) 0.0205 mol/L Concentration of Ca 2+ (mol/L) 0.01025 mol/L K sp 4.3 x 10 -6 lnK sp -12.36 ΔG° (kJ/mol) 35.81 kJ/mol Boiling Temperature Actual temperature (K) 369.55 K 1/T (1/K) 1 369.55 𝐾 Initial burette reading (mL) 22.2 mL Final burette reading (mL) 32.8 mL Volume titrated (mL) 10.6 mL Sample volume (mL) 10 mL Moles of HCl titrated (mol) 0.0199 mol Concentration of OH – (mol/L) 0.0212 mol/L Concentration of Ca 2+ (mol/L) 0.0106 mol/L K sp 4.8 x 10 -6 lnK sp -12.25 ΔG° (kJ/mol) 35.49 kJ/mol Sample Calculations M A = 0.0199 M M B = [OH-] V A = 0.0109 L V B = 0.005 L [OH-] = M A V A / V B

Trial #1 ΔH° (kJ/mol) -27.85 kJ/mol ΔS° (J/mol·K) -179.75 J/mol ·K One sample calculation: ΔH° = -(m)(R) ΔH° = - (3350)(8.314 x 10 -3 ) ΔH° = - 27.85 ΔH° from literature (kJ/mol) -12.60 kJ/mol ΔS° from literature (J/mol·K) -150.7 J/mol·K % Error in ΔH° vs literature 121.03 % % Error in ΔS° vs literature 19.28 % One sample calculation: ΔS° = Calculated result – actual result / actual result x 100 ΔS° = -179.75 - (-150.7) / -150.7 x 100 ΔS° = 19.28 % Conclusions The purpose of this lab was to find the solubility constant of the compound Ca(OH)2 at different temperatures. When completeing the calculations and comparing both calculated values of ΔH° and ΔS° to the literature values of ΔH° and ΔS°, it is clear to see that the values of ΔS° were similar to one another while the values of ΔH° were not. When calculting the percent error between both values of ΔS° the percent error between the two was 19.28%, and when calculating the percent error between both values of ΔH° the percent error between the two was 121.03%. Therefore, the calculations made for ΔS° was quite close to the reported ΔS° value while the calculations made for ΔH° was not close to the calculations made for ΔH° was not close to the reported ΔH° value . Some errors that could have caused a deviation include an error in reagent amount for example adding to little or too much, not

cleaning the equipment thoroughly to avoid contamination from one chemical to another, or not waiting enough time for the chemical to cool down after heating altering how much titration is needed. All these errors listed that could have occurred in the laboratory could have resulted in a deviation to the results calculated.